The conifer forest in southwest China is the key habitat for the giant panda (Ailuropoda melanoleuca) and vital for ecosystem services, but is being degraded by livestock grazing. Grazing influences soil environment and biota through top-down control of aboveground-belowground systems. Despite its significance, the effects of livestock grazing on soil environment and microbial communities in forest ecosystems, particularly in biodiversity hotspots, remain underexplored compared to aboveground system. Using fence experiments and structural equation models, our study identified three key mechanisms through which livestock grazing affects soil environments and microbial dynamics in a primary coniferous forest in southwest China. Livestock grazing boosted soil bacterial diversity, and altered soil properties (reducing soil organic matter and increasing pH), which indirectly suppressed bacterial diversity and diminished the prevalence of the dominant fungal group, Basidiomycota. The decreased dominance of Basidiomycota fostered greater diversity, with increased representation of subordinate groups like Ascomycota and Actinobacteria, which suggested a significant "dominance effect" within soil microbial communities. The rapid response of soil environments and microbial diversity to short-term fencing experiments suggests that rotational grazing management could be beneficial for soil ecosystem restoration. We recommend incorporating soil and microbial indicators, such as Basidiomycota's relative abundance, into conservation monitoring to track soil recovery. Short-term monitoring of these indicators allows for timely assessment of grazing management, enabling quick strategic adjustments to prevent irreversible long-term degradation. Continued monitoring of microbial shifts in relation to functions like forest growth and litter decomposition is essential for understanding the ecological consequences of livestock disturbance.

Soil salinity poses a serious threat to global agricultural development, as it severely impacts the mineralization of nutrients, especially phosphorus, and hinders the normal growth of plants. Vermicompost significantly improved the chemical properties of saline-alkali soil, changed the soil microbial community and increased the nutrient uptake of plants. This study compared the effects of two vermicompost application methods, namely fully incorporated (40.27 g pot⁻¹) and concentrated in the root-zone application (6.04 g pot⁻¹), on phosphorus availability in saline soil. Vermicompost improved the bioavailability and uptake of phosphorus in the saline soil, especially with root-zone application. The root-zone treatment significantly increased the availability of phosphorus, including Resin-P (16.0 mg kg⁻¹ compared to 6.47 mg kg⁻¹ in the mixed treatment), NaHCO₃-Pi, and NaOH-P (6.21 mg kg⁻¹ vs 5.21 mg kg⁻¹), while reducing the content of Conc.HCl-P. Vermicompost concentrated in the root zone significantly reduced soil salinity around the roots, promoted the transformation of stable phosphorus into secondary active and active fractions, and significantly improved both phosphorus availability in saline soil and plant phosphorus use efficiency. Vermicompost application also increased the abundance of phosphorus-solubilizing bacteria, Saccharothrix, Lysinibacillus, Massilia and Ohtaekwangia with root-zone application than the control and fully-incorporated treatment. In addition, the root-zone treatment significantly improved maize shoot and root biomass, enhanced phosphorus and potassium uptake, and reduced the Na⁺ to Ca²⁺ ratio, thereby limiting salt translocation to roots. This study highlights the potential of root-zone application of vermicompost to improve saline-alkali soil, enhance crop growth, and elucidate phosphorus fractions transformation mechanisms driven by microbiota.

Microbial and plant residues are primary sources of soil organic carbon (SOC). However, limited research is available on their differential contributions and influencing factors to SOC accumulation in grassland soils. Here, we collected soil samples from meadow steppe (MS), typical steppe (TS), and desert steppe (DS) across the Qinghai-Xizang Plateau, Loess Plateau, and Inner Mongolia Plateau. The distributions of microbial- and plant-derived carbon and their contributions to SOC were analyzed using amino sugars and lignin phenols (LPs) biomarkers. The relationships between microbial- and plant-derived carbon with climate, vegetations, and soil properties were explored. The results showed that microbial necromass carbon (MNC) and LPs contents were higher in MS and TS than in DS. The ratio of MNC to SOC (39.0%–54.2%) was higher whereas the ratio of LPs to SOC (1.49%–4.44%) was lower in MS and TS than in DS. Furthermore, fungal necromass carbon (FNC) accounted for larger proportion (35.1%–50.3%) than bacterial necromass carbon (BNC) (3.61%–5.87%) in SOC. Redundancy analysis identified complexed iron and aluminum oxides as the most significant factor impacting MNC and LP contents. Structural equation modeling demonstrated that mean annual precipitation and temperature influenced MNC and LPs contents by affecting vegetation biomass and soil properties (pH, silt and clay, and iron and aluminum oxides), which subsequently affected SOC accumulation. The findings suggested that MNC was the dominant source of SOC in grassland soils, with FNC contributing more to SOC accumulation. Complexed iron and aluminum oxides promoted accumulation of MNC and LPs through chemical protection.

Microplastics (MPs), as a novel global pollutant, are abundant in agricultural soils due to their recalcitrant nature. However, the key drivers regulating MPs mineralization and their impact on soil organic carbon (SOC) decomposition remain unclear. Here, we conducted a meta-analysis to estimate the mineralization rate of MPs in soil and their priming effect (PE) on SOC decomposition. We found that MPs mineralization rate was 0.114% per day, mainly mediated by MPs characteristics (chemical composition and particle size) and soil pH. MPs input simultaneously induced a significant positive PE, accelerating SOC decomposition by 33.6% on average. This process was primarily regulated by soil carbon (C):nitrogen (N) ratio and pH, and there was a significant correlation between MPs mineralization and PE. Furthermore, dissolved organic C and microbial biomass C and N in soil increased after MPs input, while nitrate decreased. These results indicated that the positive PE induced by MPs may be driven by soil microbial co-metabolism and N mining. Collectively, our findings emphasize the crucial role of MPs in terrestrial biogeochemical cycles and provide an improved assessment of SOC turnover under the global MPs crisis.

Soil microbes are of vital importance in crop function and nutrient utilization. However, the core mechanisms and contributions of rhizosphere microbiota for potassium-efficient wheat varieties remain ambiguous. This article examined 24 wheat varieties, by which significant differences in rhizosphere microbial diversity and structure between potassium-efficient and -inefficient groups have been observed. It is revealed that both bacterial and fungal communities have strong correlations with wheat potassium utilization efficiency (KUE). Furthermore, this correlation is more bound up with the abundant taxa than the rare taxa. Notably, bacterial communities are demonstrated to have more substantial associations with yield and KUE compared to its counterpart, i.e., fungal and archaeal communities. The potassium-efficient group exhibited a more complex microbial network, where bacteria occupied a more prominent ecological niche than those of fungi and archaea. Core microorganisms, primarily Bacillus and Pseudobacillus, enhance wheat KUE directly or indirectly by shaping key microbial consortium and soil microbial communities. The experiment showed that soil microorganisms make a difference in the growth and nutrient accumulation of wheat. And core microorganisms significantly facilitate wheat growth and reinforce efficient potassium nutrient absorption and utilization. This study highlighted the rhizosphere microbiome differences among wheat varieties with different potassium utilization capacities, identified and characterized the core microorganisms in the rhizosphere of potassium-efficient wheat, and revealed their potential to improve wheat potassium nutrient uptake and utilization. These findings provide valuable insights for developing wheat breeding strategies aiming at enhancing potassium utilization.

Soil microbial communities play a crucial role in maintaining multiple soil functions in terrestrial ecosystems. However, evidence linking soil microbial communities to soil multifunctionality under warming and precipitation changes remains limited. In this study, we conducted a three-year climate change experiment in a semi-arid grassland to explore the effects of warming (using open top chambers) and precipitation change (increased or decreased by 40%), as well as their interactive effects on soil microbial communities and multifunctionality. Our results indicated that the impacts of climate change became more pronounced in the third year compared to the first year after the experimental treatments were initiated. In addition, warming amplified the negative effects on soil microbial diversity, interactions, and multifunctionality under increased precipitation. Notably, the combination of warming and increased precipitation negatively impaired soil multifunctionality by intensifying competition between bacteria and fungi. Our results show that the structure of soil microbial communities, network complexity, and multifunctionality were more sensitive under the concurrence of warming and increased precipitation in semi-arid grasslands, due to their long-term adaptive mechanisms to dry environments. Therefore, it is essential to incorporate the interactions among soil microbes into future predictions of soil multifunctionality under complex climate change scenarios in semi-arid grasslands.

Despite the recognized benefits of diverse vegetation for terrestrial biodiversity and ecosystem services, its role in island ecosystem restoration remains poorly understood. We established five artificial vegetation types (grassland, windbreak and sand fixation, shelterbelt, public green space, roadside trees) on tropical coralislands and compared their soil properties and microbial communities with those of native forests. Artificial vegetation showed different levels of soil properties (except total potassium), microbial biomass (excluding fungi), enzyme activities, diversity indices (excluding fungi). Additionally, the community composition and network structure of soil microbes in artificial vegetation were distinct from those in native forests. Both ecosystems exhibited co-limitation by carbon and phosphorus. Fungi dominated in early restoration stages, while bacteria emerged as keystone drivers in later phases. Initial fungal inoculation accelerated vegetation establishment, and late-stage labile carbon inputs enhanced bacterial-mediated ecosystem stability. Phosphorus supplementation is recommended to alleviate nutrient co-limitation given that phosphorus is indispensable for microbial growth. Future research should focus on long-term dynamics to better assess restoration sustainability.

Proglacial lake is an emergent source of the second most important greenhouse gas methane as the climate continues to warm, and syntrophic bacteria play a crucial role in the sediment organic matter degradation and methane production. However, our understanding of syntrophic bacteria in the proglacial lake sediments is limited. Here, we combined 16S rRNA gene amplicon sequencing, metagenomics, and metatranscriptomics to explore the diversity, function, and activity of syntrophic propionate- and butyrate-oxidizing bacteria (SPOB and SBOB) in sediments of a glacier-fed proglacial lake on the south Qinghai-Tibet Plateau. We identified a diverse array of putative SPOB and SBOB with pronounced spatial and temporal variations, many of which were central in microbial co-occurrence networks. The most abundant SBOB were Syntrophus, Syntrophorhabdus, and unclassified_Syntrophales, and the dominant SPOB included unclassified_Syntrophobacterales, Smithella, and Syntrophobacter. Lake hydrology, water depth, and associated physicochemical properties shape the spatial patterns of sediment syntrophic bacterial communities. Genome-resolved metagenomics revealed 21 and 4 genus-level novel lineages for SPOB and SBOB, respectively. Transcriptomic evidence highlighted high activity of the uncharacterized genera UBA1429 (Anaerolineae) and E44-bin15 (Dehalococcoidia) in propionate oxidation, and JAPLJM01 (Syntrophia) as a dominant player in butyrate oxidation. This study provides the first insight into syntrophic oxidizers in proglacial lake sediments, advancing our understanding of carbon cycling and methane emission in cryosphere aquatic ecosystems.

Biological nitrogen fixation (BNF) facilitated by diazotrophs, which convert N₂ to ammonia, plays a key role in nutrient supply of terrestrial ecosystems. However, the differential contributions of rare versus abundant subcommunities to nitrogen fixation dynamics remain poorly characterized, especially in alpine ecosystem. This study examined BNF changes and shifts in abundant and rare soil diazotrophic taxa along an aridity gradient (arid, semi-arid, semi-humid, and humid) across the Tibetan Plateau. We found a significantly higher N fixation rate, vegetation coverage and biomass, nifH gene abundance, and diazotroph diversity in semi-arid and arid habitats than in semi-humid and humid habitats. Rare subcommunity composition explained more of the variation in N fixation rates than did the abundant subcommunities, suggesting greater roles of diazotrophic rare taxa in supplying nitrogen availability in alpine grasslands. The main influence factors of nitrogen fixation are aridity, plant coverage and soil C:N ratio. Structural equation modeling indicated that soil factors (e.g., bulk density, C:N ratio) and climatic factors (aridity and temperature) affected the composition of rare subcommunity through altering plant coverage and biomass, consequently affecting soil nitrogen fixation. This study establishes rare diazotrophs as critical regulators of soil nitrogen fixation and deciphers their mediation in climate-altered N-cycling processes in alpine ecosystems.

Denitrification is the primary contributor to soil N₂O emissions. Although bacterial denitrification has been extensively studied in diverse ecosystems, the contribution of fungal denitrification to soil N₂O emissions in karst areas remains unexplored, especially after vegetation restoration. In this study, we compared cropland (control) with a naturally restored forest (60 years old) by collecting 24 soil samples from both land use types. We analyzed the abundance, community structure, and contribution to soil N₂O emissions of denitrifying fungi under different land use types using inhibitor methods, quantitative PCR (qPCR), and Illumina MiSeq sequencing. We found that after vegetation restoration, the abundance of nirK-containing denitrifying fungi (7.72 × 10⁹ ± 1.82 × 10⁹ copies g^–1) was nearly threefold higher than in cropland (2.61 × 10⁹ ± 0.29 × 10⁹ copies g^–1). Moreover, vegetation restoration markedly altered the community composition of nirK-containing denitrifying fungi, leading to an enrichment of Fusarium, Trichoderma, Chloridium and Aspergillus. Additionally, the contribution of fungal denitrification to N₂O emissions was greater after vegetation restoration (35.40%) than in cropland (28.70%). Furthermore, the increase in fungal nirK-derived N₂O after vegetation restoration was closely related with high soil nitrate nitrogen (NO₃^–-N) and sand. Our research underscores the significance of fungal denitrification in driving soil N₂O emissions after vegetation restoration in karst areas.

Biochar and nitrogen (N) fertilizer are widely used to improve crop growth and rebuild soil organic carbon (SOC). However, N fertilizer and biochar addition affect SOC unpredictably because of varying effects on soil autotrophic (Ra) and heterotrophic respiration (Rh). To clarify the influence, a field experiment was conducted in which biochar was input alone at rates of 0, 3, 6, and 12 t ha⁻¹ (BC0, BC3, BC6, and BC12) and in combination with urea at 200 kg N ha⁻¹ (BC0U, BC3U, BC6U, and BC12U). Biochar alone had a negligible effect upon Ra regardless of its rate, whereas individual N fertilization promoted Ra by 62.6% than BC0. Conversely, combined N and biochar decreased Ra by 25.9%‒48.2% relative to BC0U, suggesting that biochar and N antagonistically affect Ra. In contrast to Ra, Rh was unresponsive to N alone but showed a significant elevation under biochar at rates of 6 and 12 t ha⁻¹. N fertilization, however, stimulated Rh by 12.1%‒17.7% in biochar-amended soils, suggesting that biochar and N addition synergistically affect Rh. Microbial community analyses indicated that the increased Rh under the incorporation of biochar and N fertilizer might be attributed to the stimulation of copiotrophic microbes. The lowest Rh/SOC ratio was found in BC3U, suggesting a relatively low decomposition rate of SOC. This study highlights that Rs components exhibit distinct responses to individual N fertilization, biochar amendment and their interaction, and suggests that incorporating biochar at the rate of 3 t ha⁻¹ in N-fertilized soil may potentially enhance soil carbon sequestration.

Soil aggregate formation and stability are influenced by soil organic carbon (SOC), Fe/Al oxides, and microbial activity, yet the underlying mechanisms in long-term greenhouse vegetable cultivation remain unclear. This study, conducted over 15 years in Xinmin, Liaoning, and utilized nuclear magnetic resonance and metagenomic sequencing to investigate the microbial-driven synergistic effects of Fe/Al oxides and organic carbon on soil aggregate stability. Results showed that greenhouse cultivation promoted the formation and stability of macroaggregates (>0.25 mm), with Al oxides playing a more critical role than Fe oxides. Fe oxides (Feo, Fep, Fed) primarily drove microaggregate (0.25–0.053 mm) formation, while microbe-mediated mineral-associated organic carbon (MAOC) facilitated the transformation of clay-sized fractions (<0.053 mm) into larger aggregates. However, long-term greenhouse cultivation weakened these effects, leading to a decline in macroaggregate content and stability. Long-term cultivation increased active Fe/Al oxides, key SOC components, and microbial biomass (e.g., Actinomycetota, Mucoromycota). This study is the first to elucidate the dominant role of Al oxides in macroaggregate formation and the microbial-driven MAOC mechanism promoting aggregate transformation, revealing the dynamic effects of long-term greenhouse cultivation. These findings provide a scientific basis for optimizing greenhouse management and enhancing vegetable yields.

Soil protists, as critical components of soil microbial communities, play key roles in nutrient cycling and ecosystem functioning in drylands. However, the mechanisms through which increasing aridity influences their diversity and contribution to ecosystem multifunctionality remain poorly understood. To address this, we investigated soil protist richness at 14 sites along a natural aridity gradient in northern China and evaluated its relationship with ecosystem function. We found that increased aridity significantly reduced protist richness (R² = 0.296, P < 0.001), including consumer (R² = 0.413, P < 0.001), parasitic (R² = 0.302, P < 0.001), and phototrophic groups (R² = 0.188, P < 0.001) and altered soil protist community composition (PERMANOVA, P < 0.001). Protist richness (R² = 0.264, P < 0.001) and the richness of each functional group (all P < 0.001) were positively correlated with ecosystem multifunctionality, but these richness-ecosystem multifunctionality relationships were weakened by increasing aridity (all P < 0.05). Our results suggested that aridity directly reduced protist biodiversity and disrupted its contribution to ecosystem functioning. These findings highlight the importance of addressing drought-driven biodiversity loss and its cascading effects on soil ecosystem functions in dryland management strategies.

The nitrogen (N) input can exert a dual effect on litter decomposition, depending on the litter quality. Additionally, increased N input alters plant nutrient composition, which directly impacts plant residue decomposition. However, this effect remains understudied, particularly in grassland ecosystems. We obtained two types of Leymus chinensis litter (low-N and high-N) from a long-term N addition experiment. A 730-day litter decomposition experiment was conducted to examine mass loss, nutrient release, stoichiometric changes, and microbial community dynamics. The results show that N addition increased litter mass loss by approximately 10.55%, and the mass loss of low-N litter increased by 10.14%. Furthermore, acid-unhydrolyzable residue accumulated over time, with greater accumulation in high-N litter, which may be a key factor underlying the slower decomposition of high-N litter. Another key factor may be the persistently high N:P ratio in high-N litter during decomposition, potentially making it more susceptible to P limitation. Our findings highlight that changes in litter quality under exogenous nutrient inputs play a key role in regulating decomposition, offering insights to improve predictive models of litter decomposition under changing nutrient inputs.

Soil microbiomes in urban green spaces (UGSs) critically influence the ecological functions, human health and sustainable development of one city. In the recent decade, the frequent concern of microorganisms in UGSs allow us to systematically review the research progress and focus the key questions for this field. We first summarized microbial major taxa and their distribution patterns in UGSs from local, regional and global scales, further identifying the main assembly mechanisms. We propose a three dimensional (3D) interactive framework “resource competition‒environmental filtering‒anthropogenic stress” that governs assembly of soil microbiomes in UGSs, and drives their homogenization. We then explore the relationship between UGSs soil microbiomes and critical ecosystem processes, including plant growth, carbon-nitrogen cycling and ecosystem stability. We also analyze the potential pathways through which UGSs soil microbiomes influence human health, including indirect impacts through regulating soil environmental quality, as well as direct involvement in human immune regulation. Future directions might be prioritized in monitoring soil microbiome dynamics, analyzing soil microbiome functional networks and constructing microbial-based strategies for synergistic optimization of UGSs ecology and public health.

Temperate grasslands represent a major component of the global carbon cycle, serving as significant carbon sinks. Much of this carbon storage occurs in the form of soil organic carbon (SOC). Microbial necromass carbon (MNC) is considered to be a major contributor to SOC in temperate grasslands. However, it remains unclear how nitrogen (N) and/or phosphorus (P) enrichment influence the formation and stabilization of mineral-associated organic carbon (MAOC) via MNC turnover and mineral-organic interactions. Here, based on a 12-year in situ nutrient addition experiment, we found that the simultaneous addition of N and P significantly increased MAOC. Although N and P addition reduced MNC, the retained high proportion of MNC within SOC and the decreased C/N ratio of mineral-associated organic matter (MAOM) directly demonstrate MNC dominance in MAOC formation. Our findings reveal that MNC is more readily enriched in fine-sized minerals (0–20 µm, fine silt and clay), facilitating the formation of stable MAOC. As finer fractions approach their capacity to associate with organic matter, coarser silt (20–50 µm) may represent a potential secondary sink for MNC accumulation, as indicated by their positive correlation with the proportion of MNC in SOC. This process is likely facilitated by nutrient-driven increases in ion concentrations and enhanced mineral-organic binding through metal oxide and cation complexation. Altogether, these results contribute to understanding how nutrient enrichment alters the dynamics of polyvalent cations and subsequently influences MAOC formation, highlighting the importance of mineral-organic interactions in promoting carbon sequestration and stabilization within temperate grassland ecosystems.

Soil microbial communities are important to nutrient cycling and rice plant growth. Increasingly frequent extreme climate events pose a severe threat to the stability of soil microbial communities, yet the consequences of a catastrophic microbial disturbance on rice seedling stage remain poorly understood. Therefore, we used a gamma-sterilization experiment to eliminate the native microbiome and investigate its functional importance for rice seedlings under four N input levels (0, 50, 100, and 200 mg N kg⁻¹). Amplicon sequencing showed that sterilization showed more significant impacts than N input on microbial diversity and composition. Sterilization reduced alpha diversity, enriched copiotrophs, and suppressed oligotrophs, while increasing unclassified fungal taxa. Microbial communities in non-sterilized soils were resilient to N addition, likely due to fertilization legacy. Rice biomass declined significantly in sterilized soils under low N, indicating the critical role of indigenous microbes in nutrient acquisition. Correlation analyses revealed distinct rice biomass associated taxa among treatments, suggesting disrupted plant–microbe interactions. Although the relative abundance of plant growth-promoting taxa increased in sterilized soils, their enrichment did not compensate for the loss of indigenous microbial community functions. These findings highlighted the ecological importance of native soil microbiota in supporting rice growth under variable N inputs and provided insights for nutrient management.